Power transmission

Abstract

This power transmission device, which cuts off torque that drives a vehicle, comprises: a clutch including a rotational solid capable of receiving torque and rotating about an axis, a clutch member that engages with the rotational solid and can move in an axial direction, and clutch teeth capable of connecting the clutch member and transmitting the torque; a solenoid that generates a magnetic flux in response to power input; a stator that is coupled to the solenoid so as to guide the magnetic flux and is stopped from rotating around the shaft; a rotor that is disposed so as to receive the magnetic flux from the stator and that causes rotational motion around the axis due to the received magnetic flux; and a conversion mechanism that is drivenly connected to the rotor and that converts the rotational motion into linear motion in a direction along the axis, the conversion mechanism including a thrust member that transmits the linear motion to the clutch member.

Description

[Technical field]

[0001] The following disclosure relates to a power transmission device that can disconnectably transmit torque for driving a vehicle, and in particular to a power transmission device that is integrally provided with an actuator that can drive a clutch to both engage and disengage. [Background technology]

[0002] Rotating machines used in vehicles often utilize clutches to selectively activate and deactivate their functions. For example, a so-called lock-up differential has a built-in dog clutch that is normally disengaged to allow differential motion between the output shafts, and locks the differential when the dog clutch is engaged by an external actuator.

[0003] Actuators such as hydraulic cylinders, cam mechanisms using motors, or solenoid actuators can move linearly, making them easy to use for the purpose of engaging and disengaging dog clutches. The actuator must be kept stationary relative to the rotating mechanism, and requires considerable dimensions, so actuators using hydraulic cylinders or motor cam mechanisms require a structure that protrudes significantly laterally from the axis of the rotating machine. This is a factor that restricts the design of the vehicle body. In addition, mounting the entire system to the vehicle body requires, for example, a process of mounting the actuator, a process of mounting the rotating machine body, and a process of connecting these, making the mounting work extremely troublesome.

[0004] Solenoid actuators have been devised that can be coaxially mounted with a rotating machine, are compact, and can be handled as a whole. Patent Documents 1 and 2 disclose related techniques. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Patent Application Publication WO2016 / 035129A1 [Patent Document 2] International Patent Application Publication WO2018 / 109874A1 Summary of the Invention

[0006] Although solenoid actuators have many advantages, there is a problem that their operation does not necessarily correspond to the state of the clutch. That is, even if power is applied to the actuator, the clutch may fail to engage in rare conditions such as when the clutch teeth happen to be in an inappropriate position for meshing. Even if the power is cut off, the clutch teeth may temporarily stick together due to the viscosity or magnetization of the lubricating oil, which may hinder disengagement. Therefore, in order to prevent unexpected operation, an additional device is often required to detect whether the clutch is engaged. However, as can be seen from each figure of Patent Document 2, the detection device requires an additional element on the carrier side, which requires installation independent of the differential body, ultimately reducing the utility of the solenoid actuator.

[0007] The device disclosed below has been devised in consideration of the above problems.

[0008] According to one aspect, a power transmission device that disconnectably transmits torque for driving a vehicle includes a clutch including a rotating body that receives the torque and can rotate around an axis, a clutch member that engages with the rotating body and is movable in the axial direction, and clutch teeth that can connect with the clutch member to transmit the torque; a solenoid that generates magnetic flux in response to the input of power; a stator that is connected to the solenoid so as to guide the magnetic flux and is prevented from rotating around the axis; a rotor that is disposed to receive the magnetic flux from the stator and generates rotational motion around the axis by the received magnetic flux; and a conversion mechanism that is drivingly connected to the rotor and converts the rotational motion into linear motion in a direction along the axis, the conversion mechanism including a thrust member that transmits the linear motion to the clutch member; and a differential gear set having a pair of side gears that differentially output the torque, the clutch teeth being formed on one of the pair of side gears or an inner casing that supports the differential gear set. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a partially exploded perspective view of a lock-up differential and actuator combination. [Diagram 2] FIG. 2 is a cross-sectional elevation view of the lock-up differential and actuator combination taken from line II-II of FIG. [Diagram 3] FIG. 3 is a cross-sectional elevation view of a free running differential and actuator combination. [Figure 4] FIG. 4 is an exploded perspective view of an axial gap motor in the actuator shown in FIG. [Diagram 5] FIG. 5 is a cross-sectional elevation view of an axial gap motor based on another example. [Figure 6] FIG. 6 is a cross-sectional elevation view of a radial gap motor according to still another example. [Figure 7] FIG. 7 is an enlarged sectional elevational view of the actuator in FIG. [Figure 8] FIG. 8 is a partially exploded perspective view of a lock-up differential and actuator combination according to another embodiment. [Figure 9] FIG. 9 is a cross-sectional elevation view of the combination shown in FIG. [Figure 10] FIG. 10 is a cross-sectional elevation view mainly showing an example of an actuator having a mechanism that utilizes a screw. [Figure 11] FIG. 11 is a cross-sectional elevation view mainly showing an example of an actuator using a cam mechanism. [Figure 12] FIG. 12 is a perspective view, with some parts omitted, showing a combination of a lock-up differential and an actuator that uses a mechanism that utilizes a roller screw. [Figure 13] FIG. 13 is a cross-sectional elevation view mainly showing an example of an actuator having a mechanism that utilizes a roller screw. [Figure 14] FIG. 14 is a sectional elevation view mainly showing another example of an actuator having a mechanism that utilizes a screw. [Figure 15]FIG. 15 is a cross-sectional elevation view mainly showing an example of an actuator using a ball cam mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Some exemplary embodiments will be described below with reference to the accompanying drawings. In the following description and the appended claims, unless otherwise specified, the axis means the central axis of the stator and the rotor, and usually coincides with the rotation axis of the rotor and the shaft connected to the rotor. It should be noted that the drawings are not necessarily drawn to scale, and therefore the mutual dimensional relationships are not limited to those shown in the drawings.

[0011] The combination of the clutch and actuator disclosed below can be suitably combined with a rotating machine constituting a vehicle to form a power transmission device, and can be used in particular for the purpose of controlling the function of the clutch by engaging and disengaging it from outside the rotating machine. When the clutch is engaged, the torque for driving the vehicle is transmitted via the clutch, and when the clutch is disengaged, it is disconnected. As will be understood from the following explanation, since the rotation angle of the actuator is correctly reflected in the position of the clutch member, the desired clutch state, such as engaging and disengaging the clutch, can be realized by appropriately controlling the rotation angle of the actuator by rotating it forward or backward.

[0012] The present invention can be applied to various rotating machines, one example of which is a differential that differentially distributes torque to left and right axles. A differential often has a built-in dog clutch to control its operation, which is driven from the outside by an appropriate actuator. On the other hand, the space for mounting a differential on a vehicle is limited, and the whole system including the actuator needs to be compact, so the actuator according to the present disclosure can be suitably used. For example, Figures 1 and 2 show an example in which the differential is combined with a so-called lock-up differential, and Figure 3 shows an example in which the differential is combined with a so-called free-running differential.

[0013] Referring mainly to FIG. 2 in combination with FIG. 1, the differential 3 is a rotating body equipped with a clutch 10 therein, capable of rotating T around an axis X. The differential 3 includes a differential gear set 21 coupled to a case 15 thereof, and the differential gear set 21 includes side gears 23 and 25, which are each coupled to an axle. In other words, the differential gear set 21 serves as a medium for distributing the torque received by the case 15 to the side gears 23 and 25 while allowing differential motion. FIG. 2 illustrates a bevel gear type as an example, but of course other types such as a face gear type or a planetary gear type may also be used.

[0014] In this example, the clutch member 11 capable of transmitting torque from the case 15 is movable in the axial direction, and the side gear 23 is provided with clutch teeth 13 and can be connected to the clutch member 11 as shown in Fig. 7, for example, and the combination of the clutch member 11 and the clutch teeth 13 constitutes the clutch 10. When the actuator 1 drives the clutch member 11 to connect the clutch 10, the side gear 23 temporarily becomes one with the case 15 and transmits torque. At this time, the other side gear 25 cannot perform differential motion with respect to the side gear 23, so the differential 3 is in a so-called differential-lock state in which it has lost its differential action. When the actuator 1 disengages the clutch 10, the differential 3 differentially distributes the torque received by the case 15 to both axles.

[0015] 3, the case of the differential 3 is divided into an outer case 15 that receives torque and an inner case 17 that is coaxial with the outer case 15 and can rotate relatively thereto. In this example, a differential gear set 21 is coupled to the inner case 17, and, for example, one end of the inner case 17 is provided with dog teeth to form the clutch 10. When the actuator 1 engages the clutch 10, torque is transmitted from the outer case 15 to the inner case 17, and is further distributed differentially to both axles via the differential gear set 21. When the actuator 1 disengages the clutch 10, the differential gear set 21 does not receive torque from the outer case 15, and both axles are freed from the power system.

[0016] Of course, the applications are not limited to these. Based on the present disclosure, a wide range of rotating machines can be realized that include a dog clutch, such as a transmission, a power transfer unit (PTU), or a coupling device. In addition, the clutch is, for example, a so-called dog clutch with dog teeth, but other types of clutches such as claw clutches, or more generally, clutches that transmit torque by meshing structures rather than friction, may generally be used.

[0017] In all of the embodiments described below, the actuator is combined with a dog clutch, so simple linear motion is sufficient. Nevertheless, each embodiment utilizes a hollow shaft motor that produces rotational motion rather than linear motion. The advantages of this will become clear from the following description.

[0018] 1, for example, the actuator 1 that drives the clutch 10 generally includes a hollow shaft motor 5 that generates a rotational motion R about an axis X, and a conversion mechanism 7 that converts the rotational motion R into linear motion in a direction along the axis X. The entire actuator 1 is coaxial with a rotating machine such as a differential 3, particularly with a boss portion 19 thereof, and is disposed, for example, close to or in contact with one end face of the rotating machine.

[0019] 7 in combination with FIG. 1, the motor 5, or the conversion mechanism 7 as illustrated in FIG. 9, may be housed in a housing 9, and the housing 9 is engaged with a carrier on the vehicle body side to prevent rotation. The rotation prevention can be realized by a relatively simple structure, and for example, as illustrated in FIGS. 2, 3, and 5, it would be sufficient to have a tab 55 fixed to the outer periphery of the housing 9 engaged with the carrier. The tab 55 may extend radially outward as illustrated in FIG. 2, or may extend axially as illustrated in FIGS. 3 and 5. The tab 55 may be fixed to another part of the housing 9, or may be engaged without being fixed. Of course, the housing 9 may have some structure that directly engages without using a tab, and the other party of the engagement may be an element other than the carrier.

[0020] The housing 9 may also be fitted into the boss portion 19, and may also be in contact with or fitted into the end face of the case 15. Correspondingly, the end face of the case 15 may be provided with a structure that fits with the housing 9, for example a circumferential groove recessed so that the housing 9 can be partially fitted into, or a flange extending from the end face and partially fitting into the outer periphery of the housing 9. These structures provide stability to the motor 5 and conversion mechanism 7 supported by the housing 9, and are also advantageous for handling the entire device as a whole.

[0021] The housing 9 is slidably fitted to the boss portion 19, and a very small gap is maintained between them to allow lubricating oil to be trapped. In order to retain the lubricating oil, an oil groove may be formed on the inner circumference of the housing 9, on the outer surface of the boss portion 19, or on both of them. Alternatively, as shown in Figs. 10, 14, and 15, a bearing 63 may be interposed between the housing 9 and the boss portion 19. Since the actuator 1 does not generate a large thrust force, a ball bearing may be applied to the bearing 63 as shown in Figs. 14 and 15, or a needle bearing as shown in Fig. 10 may be used, or of course, another type of bearing may be used. Alternatively, instead of or in addition to the bearing, a solid lubricant may be used, or a low-friction coating such as polyfluoroethylene may be applied to either or both of the housing 9 and the boss portion 19.

[0022] For example, referring to FIG. 4, the motor 5 generally includes a solenoid 31 that generates a magnetic flux F in response to the input of electric power, a stator 33 that introduces the magnetic flux F, and a rotor 35 that generates a rotational motion R about an axis X by the received magnetic flux. The solenoid 31 may be a single electromagnetic coil, or may be a group of multiple coils 31c arranged in a circumferential direction about the axis X. Each coil 31c may be wound around a core 33c made of, for example, a soft magnetic material in order to efficiently extract the magnetic flux F. The cores 33c may be connected to each other to form an integrated stator 33, or may be separate from each other to form the stator 33. The solenoid 31 and the stator 33 may be integrated. The stator 33, together with the solenoid 31, is prevented from rotating about the axis X relative to the housing 9, and is preferably immobilized in the axial direction as well.

[0023] The rotor 35 is made of a magnetic material, is a substantially cylindrical body symmetrical about the axis X, and can perform rotational motion R about the axis X without being prevented from rotating. The rotor 35 is disposed slightly apart from and facing the stator 33 in the direction of the axis X so as to be able to receive the magnetic flux F guided from the stator 33. Although only a combination of a single rotor 35 and a single stator 33 is illustrated in FIG. 4, in order to increase the driving force, a pair of rotors 35 may sandwich the stator 33, or a pair of stators 33 may sandwich the rotor 35, or further, two or more pairs of stators 33 and rotors 35 may be arranged in the axial direction.

[0024] The stator 33 and the rotor 35 may each have a flat surface on the opposing surfaces as shown in Fig. 10, but may each have a three-dimensional structure to increase the area through which the magnetic flux passes. One example of such a structure is one in which concentric ribs rise from each and are intertwined, as shown in Figs. 4 and 5, but this is of course not limited to this. Such a structure contributes to an increase in torque or to improving the efficiency of power utilization.

[0025] The stator 33 and the rotor 35 are preferably maintained in close proximity to each other. To maintain the close proximity and allow the rotor 35 to rotate smoothly, a bearing 57 such as a ball bearing may be interposed between the stator 33 and the rotor 35, as shown in Figs. 5 and 10. The arrangement of the bearing 57 in the illustrated example is advantageous for stabilizing the rotor 35 against the attractive force of the magnetic flux F. Alternatively, as shown in Fig. 6, the bearing 57 may be interposed between the housing 9 and the rotor 35. Also, as shown in Figs. 5 and 10, only one bearing 57 may support the rotor, or as shown in Fig. 6, a pair of bearings 57 may sandwich and support the rotor 35. The housing 9 may directly support the rotor 35 via the bearing 57, or may indirectly support the rotor 35 via a member (for example, the rotary member 45 described later) that is coupled to the rotor 35. In the latter case, the bearing 57 may be interposed between the housing 9 and the rotary member 45. Further alternatively, the boss portion 19 may support the rotor 35 or the rotary member 45 instead of the housing 9 , and the bearing 57 may be interposed between the boss portion 19 and the rotor 35 or the rotary member 45 .

[0026] The examples shown in Figs. 4 and 5 are both examples of axial gap motors in which the rotor and stator are aligned in the axial direction, and magnetic flux F is drawn in a direction parallel to the axis. When there is a relatively larger margin in the radial direction than in the axial length, the axial gap motor is advantageous for improving output, or for miniaturization at the same output. Axial gap motors may also be arranged in tandem in the axial direction to further improve output. Of course, instead of an axial gap motor, a so-called radial gap motor may be used in which the rotor is coaxial with the stator and arranged close to the inside or outside in the radial direction, and magnetic flux F is drawn out in the radial direction, as shown in Fig. 6, for example.

[0027] For example, referring to Figs. 1, 5 and 6, the solenoid 31 is connected to an external drive circuit via a cable 37. The drive circuit generates AC or pulse currents having a phase difference and inputs them to the multiple coils 31c, thereby generating a rotational motion R in the rotor 35 as shown in Figs. 1 and 4. The direction of the rotational motion R can be controlled by the direction of the phase difference, that is, the motor 5 can generate the rotational motion R in both forward and reverse directions. A switching element can be used to generate the AC or pulse current, and the switching element can be, for example, a semiconductor element such as an insulated gate bipolar transistor (IGBT), but is not necessarily limited to this. Also, the above description relates to a so-called induction type motor, but various types such as a synchronous type, a permanent magnet type, a commutator type, and a DC type can be used instead.

[0028] 1 and 2, for example, the conversion mechanism 7 includes a thrust member 41 and is drivingly connected to the rotor 35, converting its rotational motion R into linear motion and outputting it to the thrust member 41. For the conversion, for example, a cam mechanism, a ball cam mechanism, a screw mechanism, or a roller screw mechanism can be used. The legs of the clutch member 11 extend outwardly through, for example, the end wall 15E of the case 15, and the thrust member 41 abuts against or is connected to drive it.

[0029] 1 and 2 in combination with Fig. 7, for example, according to a cam mechanism, although not necessarily limited thereto, thrust member 41 is ring-shaped and has cam surface 41c inclined in the circumferential direction on the surface facing rotor 35. Correspondingly, rotor 35 has a suitable structure for sliding on cam surface 41c. In the illustrated example, conversion mechanism 7 is near the innermost circumference of rotor 35, but it may be disposed closer to the outer periphery or near the outermost circumference.

[0030] When the rotor 35 rotates R while the thrust member 41 is prevented from rotating by the housing 9, the rotor 35 pushes up the inclined cam surface 41c, or pushes down the inclined cam surface 41c by reverse rotation, thereby converting the rotational motion R into linear motion. To smooth the sliding, a rollable roller 53 may be interposed between the rotor 35 and the cam surface 41c. In the example of FIG. 1, the rotor 35 has a pocket 35c for holding the roller 53, and as the rotor 35 rotates, the roller 53 rolls on the cam surface 41c, thereby driving the thrust member 41 in the axial direction. Instead of or in addition to the thrust member 41, the rotor 35 or a member integral therewith may have an inclined cam surface. The roller 53 may be in the shape of a cylinder or a truncated cone, for example, or may be in the form of a sphere as shown in FIG. 15. The example of FIG. 15 can be said to be a kind of ball cam mechanism, and is advantageous when a larger output is required.

[0031] The thrust member 41 may directly contact the leg of the clutch member 11, but the former is prevented from rotating and the latter rotates, so that they need to slide against each other. For convenience of sliding, a bearing 59 may be interposed between them, as shown in Figs. 9, 10, 11, 13, 14, and 15. The bearing 59 may be a ball bearing as shown in Figs. 9, 10, 11, 13, and 14, or a needle bearing as shown in Fig. 15, and of course other types may be applied. A solid lubricant may be interposed instead of a bearing, or a sliding with a lubricant or the like may be interposed. The bearing 59 and the clutch member 11 may be directly connected as shown in Fig. 10, but an appropriate tie member 51 may be further interposed between them to mediate the driving force as shown in Figs. 9, 11, 13, 14, and 15. 14 and 15, the tie member 51 may be, for example, a circumferentially continuous cylinder or ring that receives one of the races of a bearing 59 that is also circumferentially continuous. Alternatively, as shown in Figures 9, 11 and 13, the tie member 51 may be a plurality of members that are not circumferentially continuous but are arranged discontinuously in the circumferential direction. Also, one tie member 51 may be composed of a plurality of members arranged in the circumferential direction.

[0032] In the example shown in Figs. 1, 2, 7, 14, and 15, the thrust member 41 and the clutch member 11 are connected by a through hole passing through the end wall 15E in a direction parallel to the axis X, but as shown in Figs. 8 to 13, the through hole may pass through the casing 15, particularly the peripheral wall, in a radial direction. Such a structure is advantageous in that it makes it easier to manufacture the casing 15. To allow radial access, the thrust member 41 of the conversion mechanism 7 may be cylindrical, as best shown in Fig. 8, extending to cover the through hole on the peripheral wall. As shown in Figs. 8, 10, and 15, the clutch member 11 may be directly exposed from the through hole and connected to the thrust member 41, but as shown in Figs. 9, 11, 13, and 14, the clutch member 11 may not be exposed from the through hole and a tie member 51 may mediate the connection. In the latter case, the tie member 51 is one or more blocks corresponding to the respective through holes, and extends radially inward from the thrust member 41 to connect to the clutch member 11. Of course, in either of these cases, a bearing 59 can be interposed between the thrust member 41 and the clutch member 11.

[0033] In either case, the contact between the side surface of the leg or thrust member 41 of the clutch member 11 and the side surface of the through hole can be utilized to maintain the clutch engagement or to promote disengagement. For example, the side surfaces of the through hole may be inclined in the circumferential direction, and the side surfaces of the leg or thrust member 41 of the clutch member 11 that contact the through hole may also be inclined accordingly. When the inclined surfaces come into contact with each other, a part of the torque applied to the case 15 is converted into an axial force. Such a converted axial force contributes to maintaining the clutch engagement or promoting disengagement. Of course, this is not essential to each embodiment.

[0034] The cam mechanism can drive the clutch member 11 in both the direction in which the clutch 10 is engaged and the direction in which the clutch is disengaged, but generally, the clutch member 11 is relatively unreliable in the direction in which the clutch is disengaged compared to the direction in which the clutch is engaged. Therefore, an elastic body such as a spring may be used to encourage the clutch member 11 to be disengaged. In the examples shown in Figs. 7, 9, 11, and 13, a spring 61 is interposed between the side gear 23 and the clutch member 11, and biases the clutch member 11 in the direction in which the clutch member 11 is disengaged. Also, an elastic body may be used in a direction that encourages engagement, as opposed to the illustrated examples. Of course, the elastic body is not essential or specific to these embodiments.

[0035] As already mentioned, instead of the cam mechanism, the conversion mechanism 7 may use a screw mechanism using a set of threads that are screwed together, as shown in FIG. 10. The threads may be cut in a rotary member 45 that is separate from the rotor 35, and the rotary member 45 may be press-fitted or joined to the rotor 35. Alternatively, the rotor 35 may be directly threaded. The corresponding threads may also be cut in a counter member 47 that is separate from the thrust member 41, or the counter member 47 and the thrust member 41 may be integral. Alternatively, the threads may be cut only on one side, and the other may have a suitable protrusion that engages with the threads. Furthermore, instead of the threads, a helical track may be used, and rolling elements such as balls may be interposed between the tracks. In the illustrated example, the thrust member 41 is supported slidably and prevented from rotating by contacting the inner surface of a cylinder extending from the housing 9, but it may be supported and prevented from rotating by other suitable means. When the rotary member 45 (or rotor) is rotated by the motor 5, the thrust member 41, which is prevented from rotating, is pushed out along the thread, or moved backward by reverse rotation, thereby converting the rotational motion R into linear motion. Needless to say, the screw mechanism may have the example shown in FIG. 14 or various other forms.

[0036] Alternatively, a roller screw mechanism as shown in Figs. 12 and 13 can be used. Referring mainly to Fig. 13, a screw thread is cut on the rotary member 45 or directly on the rotor 35, and a roller-shaped counter member 47 is cut with a screw thread so as to screw with the rotary member 45. Each counter member 47 is axially oriented and supported at both ends by the thrust member 41, so that it can rotate. Although the thrust member 41 is omitted in Fig. 12, the counter members 47 may be arranged in the circumferential direction. The number of counter members 47 is not limited to the example shown in the figure, and may be, for example, about three symmetrically, or may be more than that. The screw thread of the counter member 47 is cut at least over a range that allows it to move in the axial direction, and the counter member 47 is pushed out along the screw thread by the rotation of the rotary member 45, or retreated by the reverse rotation, so that the thrust member 41 advances or retreats along the axial direction.

[0037] As can be understood from the above description, the screw mechanism or roller screw mechanism can drive the clutch member 11 in both the engaging and disengaging directions, so that a resilient body to assist the mechanism is not necessary. Nevertheless, a resilient body such as the spring 61 may be used.

[0038] In each of the above-described embodiments, the thrust member 41 is prevented from rotating and moves only linearly to drive the clutch 10. Alternatively, as described below, a configuration is possible in which a member that is rotated by the motor 5 also moves in the axial direction to drive the clutch 10.

[0039] According to the example shown in FIG. 11, the housing 9 that is prevented from rotating and the rotatable cam member 41a constitute the conversion mechanism 7. The conversion mechanism 7 may be a cam mechanism, a screw mechanism, or any other suitable mechanism. The rotary member 45 and the cam member 41a are connected by, for example, a spline 43, so that the rotary motion is transmitted from the rotary member 45 to the cam member 41a, and the cam member 41a is movable in the axial direction relative to the rotary member 45. When the rotary member 45 rotates, the cam member 41a advances or retreats in the axial direction by the conversion mechanism 7 while being driven by the rotation. The cam member 41a may be separate from the thrust member 41 and connected to each other as in the illustrated example, or may be integrated with the thrust member 41. According to this structure, the conversion mechanism 7 can be disposed at the outermost position in the radial direction of the actuator 1, which is convenient for, for example, disposing a sensor on the outside to monitor the state of the actuator 1. Of course, unlike the illustrated example, the conversion mechanism 7 may be disposed on the inner circumference.

[0040] FIG. 14 shows another example using a screw mechanism. A screw thread is cut on the inner circumference of a ring-shaped base 9a that is prevented from rotating, and the thrust member 41 advances or retreats along the axial direction by screwing into the screw thread. In order to transmit rotation from the motor 5 to the thrust member 41, for example, a pin or rod 45b can be used, and one or both ends of the pin or rod 45b are fixed to the rotary members 45a and 45c. The pin or rod 45b may transmit rotation by penetrating the thrust member 41, or a connection that allows axial movement, such as a key connection, may be used, as described later. The thrust member 41 rotates following the rotary members 45a and 45c, and is also movable in the axial direction. In this example, at least the rotary member 45a is exposed outward in the radial direction, which is advantageous for monitoring its rotation angle. The pin or rod 45b is parallel to the axial direction, but may be inclined as appropriate.

[0041] The thrust member 41 may be directly connected to the clutch member 11, or may be connected via a tie member 51. In this example, the tie member 51 is, for example, a substantially cylindrical member slidably fitted to the boss portion 19 of the case 15, and is connected to the thrust member 41 so as to move together at least in the axial direction. The connection may be an engagement that allows them to slide relative to each other in the circumferential direction, or a bearing 59 may be interposed, that is, the tie member 51 is rotatable relative to the thrust member 41 in the circumferential direction. At least a portion of the tie member 51 extends toward the clutch member 11 and is connected thereto. For example, a bolt may be used for the connection, but is not necessarily limited to this. With this structure, when the thrust member 41 moves in the axial direction, the clutch member 11 also moves together with the thrust member 41 in the axial direction, while the clutch member 11 is rotatable relative to the thrust member 41.

[0042] The example shown in FIG. 15 is another example. The rotary member 45 extends from the motor 5 in the axial direction and is connected to the thrust member 41. The connection is, for example, by a combination of a key and a key groove, so that the thrust member 41 rotates following the rotary member 45 and is also movable in the axial direction. A cam ball 53 is interposed between the thrust member 41 and a ring-shaped base 9a supported and prevented from rotating by the housing 9, and one or both of the thrust member 41 and the counter ring 9a have a cam surface inclined in the circumferential direction. When the rotary member 45 is rotated by the motor 5, the cam ball 53 rolls on the cam surface, and the thrust member 41 is driven in the axial direction. In this example, the clutch member 11 rotates relative to the thrust member 41, so a bearing 59 may be interposed between the thrust member 41 and the clutch member 11, and the bearing 59 may be supported by the tie member 51. In this example, at least the rotary member 45 is exposed outward in the radial direction, so that it is advantageous to monitor its rotation angle.

[0043] Also, the tie member 51 may be fixed to one of the legs of the clutch member 11 and the bearing 59, and may be detachable from the other. According to such an example, it is easy to adopt an assembly method in which the motor 5 and the conversion mechanism 7 are assembled independently and then integrated into the differential 3.

[0044] For example, as shown in Fig. 9, the conversion mechanism 7 can be disposed radially inside the motor 5, or as shown in Figs. 11 and 13, the conversion mechanism 7 can be disposed radially outside. In either case, in the actuator 1, the hollow shaft motor 5 and the conversion mechanism 7 are coaxial and can be nested so that one fits inside the other, making it compact in both the axial and radial directions. Of course, as shown in Figs. 7, 10, 14, and 15, the motor 5 and the conversion mechanism 7 may be disposed adjacent to each other in the axial direction, making the actuator 1 more compact in the radial direction and sufficiently compact in the axial direction.

[0045] As can be seen from each figure, the actuator 1 as a whole does not protrude significantly in the radial direction from the rotating machine, and is generally equal to or smaller than the range of the rotating machine in the radial direction. It should be particularly noted that the actuator 1 according to each embodiment can be made to have dimensions similar to those of a conventional solenoid actuator used in a differential, and therefore can be used interchangeably with a conventional solenoid actuator without changing the design of the vehicle body.

[0046] The actuator 1 according to each embodiment can maintain the position of the thrust member 41 without input of electric power before and after driving the clutch member 11. Therefore, no additional members or structures are required to maintain the clutch in the engaged or disengaged state. This is advantageous in increasing the freedom of design of the device, and of course, is also advantageous in reducing costs.

[0047] In addition, since the actuator 1 is not combined with a friction clutch that requires a large driving force, a material with a relatively low strength, such as resin, can be used for each member, such as the rotary member 45 and the thrust member 41. This is advantageous for preventing leakage of magnetic flux, and is advantageous for reducing power consumption. Also, for example, a resin such as polytetrafluoroethylene can be used for the purpose of reducing friction.

[0048] As can be understood from the above description, the actuator 1 can drive the thrust member 41 in both the axial direction, the engagement direction and the disengagement direction, and the clutch member 11 follows this. Since the operation of the actuator 1 and the state of the clutch 10 necessarily correspond to each other, it is sufficient to monitor the state of the clutch only by monitoring the actuator, and there is no need to provide an additional device for detecting whether the clutch is engaged or not. The state of the actuator can also be known directly from the rotation angle of the rotor. For example, since the inductance of the motor changes periodically due to the change in the positional relationship between the rotor and the stator, the rotation angle can be known by electrically counting the inductance change. Therefore, the state of the clutch can be detected by an electric circuit or software without an additional device. Of course, a structure such as an encoder may be attached to the rotor 35, and the rotation angle may be detected by a non-contact sensor, and these structures and devices can be built into the motor 5. In order to read out information to the outside, the motor 5 may be provided with a cable 39 independent of the power supply cable 37, as shown in Figs. 5 and 6. These contribute to facilitating installation in the vehicle body. Alternatively, the encoder may be attached to a member that can be exposed to the outside, such as the rotary member 45, and information may be read from the vehicle body side. Even in this case, no major design change is required on the vehicle body side, and the installation is not complicated.

[0049] In each embodiment, the rotor or rotary member is necessarily large in diameter and has a high peripheral speed, so the actuator can quickly drive the thrust member and therefore can quickly engage and disengage the clutch. This provides superior response compared to hydraulic cylinders and conventional motor cam mechanisms.

[0050] Although several embodiments have been described, the embodiments can be modified or altered based on the above disclosure.

Claims

1. A power transmission device that disconnectably transmits torque for driving a vehicle, A rotor capable of receiving the torque and rotating about an axis; a clutch including a clutch member that engages with the rotor and is movable in an axial direction, and clutch teeth that can be coupled with the clutch member to transmit the torque; A solenoid that generates a magnetic flux in response to the input of electric power; a stator coupled to the solenoid to guide the magnetic flux and fixed about the axis; a rotor disposed to receive the magnetic flux from the stator and causing rotational motion about the axis by the received magnetic flux; a conversion mechanism drivingly connected to the rotor to convert the rotational motion into linear motion in a direction along the axis, the conversion mechanism including a thrust member that transmits the linear motion to the clutch member; A power transmission device comprising: A differential gear set including a pair of side gears that differentially output the torque, A power transmission device, wherein the clutch teeth are formed on one of the pair of side gears or an inner casing that supports the differential gear set.

2. 2. The power transmission device according to claim 1, wherein at least said stator and said rotor are coaxial with said rotating body and each form a ring around said axis.

3. a housing that accommodates the solenoid, the stator, and the rotor, the housing being prevented from rotating about the shaft and preventing the stator and the thrust member from rotating; The power transmission device of claim 1 further comprising:

4. 2. The power transmission device of claim 1, wherein either or both of the rotor and the thrust member include a cam surface, a screw thread, or a helical track that is inclined in a direction to convert the rotational motion into the linear motion.

5. 2. The power transmission device according to claim 1, wherein the conversion mechanism comprises: a tie member for coupling to the clutch member; and a bearing interposed between the thrust member and the tie member to mediate the linear motion while allowing relative rotation between the thrust member and the tie member.

6. 2. The power transmission device of claim 1, wherein a combination of the solenoid, the stator and the rotor constitutes an axial gap motor in which the stator and the rotor are spaced apart in the direction of the axis, or a radial gap motor in which the stator and the rotor are spaced apart in a radial direction perpendicular to the axis.

Images